Pros
Work with some of the brightest technical minds in the industry. People are willing to collaborate in the best interest of the customer. The product quality is improving and the ability for the products to interoperate has been improved ten fold in the past 5 years. Employees have early access to beta products and well as are provided a good amount of training opportunity. Benefits are generally good. HR does try to continually improve benefis to keep Microsoft at the top. Pay is good as well in general, it does depend on role and performance. Employees who are doing outstanding work are rewarded well. Employees who are not doing well are managed out of the company (Caveat discussed below).
Cons
If you asked me these questions a year ago, I would answer differently. Due to recent changes in the review model, Microsoft is a less desirable place to work. The company has become excessively focused on metrics which detracts from focusing on the long term sucess of the company. The environment has become more cut throat and a higher stress workplace. Employees are constantly worried about being giving a low review score without much control over it. If you want control over it you need to work all of the time and then that does not even secure anything since situationalism. For instance, if your territory has budget issue in respective clients, or if upper management decisions to change review metrics part way through the year. Manager favoritism runs rampant in the company, it can have a direct impact on how well you do regardless of metrics. HR has covered themselves with a clause in the ratiing system, "In relation to your Peers." Let's say that you have a team of rock stars, not uncommon at Microsoft, of a pool of 50 people approximately 3-4 people will need to be placed into the lowest rating which means they will be on a program that will be difficult to get out of and likely asked to leave the company. Another 6 or 7 people will be rated just above the lowest ranking which will put them in a position where other groups will find them undisirable. Therefore, about 20 percent of the employees are labeled in such a way that they will have difficultly moving between organizations in the company. If you are reporting to a manager that you don't get a along with, your days will potentially be numbered.